Third consecutive SpaceX Starship test flight ends in failure - VIDEO

"Our chances of making it all the way down to the Indian Ocean are pretty slim," a SpaceX commentator said during a livestream.

There had been hopes of a successful mission, as the rocket had progressed beyond the point of explosive past failures in January and March.

But plans to release a series of mock satellites after lift-off were abandoned because its payload door failed to open fully.

The vessel had been mounted atop a Super Heavy booster that was being reused for the first time ever - and while that was meant to make a soft landing, it ended up slamming into the Gulf of Mexico.

SpaceX hopes that Starship will one day be used to ferry people and cargo to Mars, but this latest setback plunges Elon Musk's ambitions into doubt.

Failed launches earlier this year disrupted dozens of flights across the US - and the project was grounded for two months while an investigation took place.

Musk was due to update the world on his space exploration ambitions later, in a speech entitled "The Road to Making Life Multiplanetary" - but the event has been delayed without explanation.

Nonetheless, the world's richest man described the latest test flight as a "big improvement".

He also vowed to pick up the pace with future launches - and says the next three flights will take place every three to four weeks.

On X, the company added: "With a test like this, success comes from what we learn, and today's test will help us improve Starship's reliability."

NASA needs SpaceX to make huge advances with Starship over the next 12 months as the US agency tries to fulfil an ambition of landing astronauts back on the moon.

Musk had been hoping for success after pledging to start focusing on his many businesses - Tesla, X and SpaceX among them - after attempting to slash government spending while in the Trump administration.

Footage posted on social media showed the billionaire watching the test flight unfold from a control centre, while wearing the T-shirt "Occupy Mars".